Wave transmitting and amplifying



Sept. 15, 1931. R. A. HEISING I WAVE TRANSMITTING AND AMPLIFYING 2 Sheets-Shut 1 Original Filed Dec. 0. 1921 Sept. 15, 1931. R. A. HEISING WAVE rnmsurr rme um AHPLIFYI-NG 2 sheets-sheet 2 Original Filed Dec. 30. 1921 QmQ mve/vfar Ray/770 744. Ha s/b7. ky

RAYMOND A. HEISING,

Patented Sept. 15,1931

UNITED- srArEs PATENT OFFICE OI HILLBURN, NEW JERSEY, .ASSIG'NOR T WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N Y., A. CORPORATION OF NEW YORK WAVE TRANSMITTING AND AMLPLIFYING Application flled necember 30, 1921, Serial No. 525,906. Renewed November 6, 1928.

This invention relates to improvements in systems and methods of wave transmission and more particularly in radio transmitting systems. Certain features (however, are of general application and maybe employed, for example, in, receiving systems, wire transmission systems, repeaters,'.or other. apparatus employing electron discharge devices. Other features, however, are not limited in application to systems utilizing electron discharge devices but may be otherwise employed.

One object of the invention is to provide means for multiplex communication with a single antenna and in carrying out this object, use is madeof a multiply tuned antenna system, that is-a system adapted to offer low impedanceto impressed currents of differ-.

ent frequencies. Shunt paths to the antenna are provided for giving the antenna system additional degreesof freedom and an impedance or excluding circuit is included in each path to prevent the passage therethrough of waves of other frequencies.

The invention also comprehends improvements in modulating systems and methods. Use is made of an oscillatorto produce a modulated high frequency wave, and one or more amplifiers are arranged to repeat this wave. With one condition of adjustment of the amplifiers, the wave will be amplified without inaterial distortion. However, with another condition of adjustment the portions of the modulated wave ofgreatest amplitude will be amplified to reater extent than those portions of least amplitude therebjfi'effectinga further modulation as explained broad aspects of this feature are defined in the claims. Filters are provided for 4 "venting the output circuits of the ampli ers,

hereinafter in greater detail. Certain from reacting on each other by power transferred'through the antenna circuit. A further object is to provide means in radio transmitting systems for rendering the carrier frequency independent of the condition of the transmitting antenna and independent of the amplitude or wave form vof the modulating wave. In other words rapid or slow variations, either in the condition of the 4 is designed to permit the cause the element of the transmitter rent.

antenfia min the condition of the variable lmpedance'device which controls the amplitude of the transmitted waves, do not change the transmitted frequency. This is accomplished by generating a wave of relatively low power and of constant amplitude and frequ'ency, and variably amplifying this wave in a repeating device. The constant current method, of controlling the repeating device is known high frequency amplifiers have some.

measure of distorting action, a still further refinement consists in placing a filter circuit between" the last repeater. and the antemiafj This filter circuit is of importance in multiplex operation, that is, in systems where a plurality of high frequency waves are impressed upon a single radiating structure. The filter passage of a particu% lar frequency from the ampl fier to the" antenna and to suppress other frequencies tending to pass from the antenna back to the amplifier. For a similar reason, modulating systems of the kind described may bte advantageously applied in multiplex sys ems, be-

which is adj acent the transmitting antenna'is' an. amplifier which does not allow appreciable reaction from the vantenna back upon the oscillator which eneratesthe carrier frequency curhis is -not to say that such modulating systems are not useful in systems transmitting only a singlemessage at a time upon one antenna, but merely topointout a special advantage of this arrangement in connection with plural channelesystems, vThe possible reaction-betweent arious channels is thus considerably, reduce morei'mportant in multiplex high power systemsbecause a relatively slight modulating "This feature is still r 15 circuit diagram of'one of the systems being shown, the second system being outlined by rectangular blocks, and the third being merely indicated; Figs. 1a andlb show alternative arrangements 0 the auxiliary'tuning system for the antenna which may be substituted for that portion to the right of the line X-X in Fig. 1; Fig. 2 is a complete system which may be substituted for any one of the three transmission systems of Fig. 1, and F g. 31s a simplified circuit arrangement adapted to transmit modulated waves of a single frequency as well as waves oftwo frequencieseach modulated in accordance with the same signal.

, In Fig. 1,- the line L represents any circuit such as a telephone line, in which are produced low frequency signaling waves to be transmitted upon a high frequency carrier Wave. The low. frequency waves are impressed upon the input circuit of a threeelectrode electric discharge device V which typifies any variable im edance system. The anode-cathode circuit 0 the system V is supplied from the source 1 through a choke coil 2 which isadapted to prevent the passage of current variations haxng frequencies such as exist in line L. r

Assuming that the switch 3 is positioned upon the contact 3 there will be connected in parallel with the system V with respect to the source 1 and coil 2, an oscillation generating system 0, a high frequency amplifying system HA and a second high frequency 'am lifying system HA.

achof the systems V, 0, HA and HA. may consist of a single vacuum tube or equivalent device orany suitable number of vacuum tubes or equivalent functioning devices arranged in parallel. The system"Y may be .of any kind which efiiciently varies the space current of the remaining tubes of the system.

The oscillating system 0, as illustrated, is of a well-known type and generates high frequency oscillations in a tuned circuit comprising capacity 4 and inductance Space current is supplied to the system 0 througha radio frequency choke coil 6 which prevents high ,frequency variations from.

passing therethrough .and being" short circuited through the coil 2 and source 1 or either of them. Y 1

Resistance 7 serves to reduce the direct potential impressed upon the space current path of the system 0 while the capacity 8 allows speech tfrequency variations to pass readily.

The function of resistance 7 and capacity 8 is to cause the oscillations generated by the oscillator to be more completely modulated. By proper adjustment of the resistance the modulated oscillations may be made to fall to zero amplitude during each speech cycle. A further function is to cause a smaller direct current voltage to be applied to the plate circuitof the tube of the oscillator 0 than is gwplied to the tubes of the amplifiers HA and Since the space current of the oscillator will be varied inaccordancewith low frequency variations of impedance 'in the system V, the waves generated by system 0 will be modulated in accordance with these low frequency waves. y

The modulated waves produced are impressed upon the input circuitof the high frequency amplifying systemHA, of which the output circuit is connected tovthe input circuit of the second-amplifying system HA for further amplification.

Assuming that switch 8 is positioned on contact 3, the space current .of the system,-

HA will be varied in a similar manner as that of the system 0. -The amplification ratio of the system HA will, as a result of this, tend to be moderately greater at those instants when the waves supplied to its input circuit are of large amplitude thanat those instants when-the waves supplied to its input circuit are of'small amplitude. amplification of the applied high frequency will, therefore, result, tending to produce a greater disparity in the amplitude of the waves in the output circuit of the. system HA than exists in the waves supplied to the input circuit. The space current of the system HA will undergo a corresponding vari- A variable ation and the efi'ect of this systemnipon. the

waves supplied to its input circuit will be similar to that of the preceding amplifier.

By movin the switch 8 to the contact 3,

the amplifying system HA will nothave its space current supplied through the coil 2 and hence it will tend to act as an ordinary amplifier. ductive impedance for waves of signaling, i. e. speech frequencies. Source 1 and coil 2 together form a highly inductive source.

Still other means are provided whereby the systems HA and HA may bemade: to function as substantially distortionless ornonmodulating amplifiers even though 7 their space current is supplied through the coil 2.

This isaccomplished by providing in the input .circuit of each of these systems, a leak The coil 2 constitutes a high in- 1 supplied to the input circuit increases and decrease when this amplitude decreases, since this charge is at any instant due to the rate of supply of electrons from the filament combined with the rate of leakage through the resistance 9. a

When waves of relatively larger amplitude are applied to the input circuit the supply of electrons to the grid .is more rapid, hence when the amplitude of the supplied wave increases, the successive waves will cause a large leakage current to flow to the grids 11 as compared to the leakage current flowing when the amplitude is small-.- Since the amplification ratio of a discharge repeater of' thistype tends to decrease as the negative charge upon the grid increases, it will be seen that this compensates for the variation in the amplifying power caused by low frequency variations in the anode-cathode potential supplied to the tube. pensation may be varied through a wide range. by variations in the capacity 10 and the resistance 9. It will also depend upon the particular design of the vacuum tube being used. In some instances, it may be desirable to so adjust the systems HA and HA that each will effect modulation of the waves repeated thereby. In' other instances, however, it may be desirable to so adjust the'systems that the minimum of such modulation is effected. Even though no modulation is taking place in both of these systems or either of them,

there are certain advantages connected with the supplying of their space current through the choke coil 2. A important one of these advantages is that the total energy consumptionin the amplifying systems with a given high frequency energy output is reduced. The importance of the energy saving function of a system of this kind is considerable and this feature is em hasized.

I At instants, w en the amplifying tubes are amplifying high frequency waves of large amplitude, they must have a large average value of space current and when the are amplifying high frequency Waves of small amplitude, a small average. value of space currentis suflicient. This is precisely what occurs. During the portions of the cycle of the modulating frequency, when high frequency Waves .pf large amplitude are produced, the average value of the space current is propor tionally large. .When the. high frequency Waves are of small amplitude the average value of the space current issmall.

Furthermore, when the space current'has the largest average value, the average impedance of the tu-be is the smallest and when the space current. has the smallest average; value,

the impedance of the tube is, on the average,

The extent of this comev the greatest. Efficient utilization of the energy supplied to the space current path of the system results. In this discussion of" coupled to the antenna system a by inductively related coils 12 and 1,3. Coil 12 is located in a path including condenser lfl and inductance 15 which is tuned to the mean frequency generated by the oscillating system 0. Shunt paths 16 and 17 are tuned by means of inductance and capacity to offer low impedance to waves of the frequencies produced y the oscillating system 0 of transmitters T1 and T2 respectively. The energy impressed upon the coil 12 from the systems T1 and T2, is thus short-cireuited through the paths 1(5 and 17 and is not impressed to a material extent upon the space current path of the amplifier HA"; In this manner, interl'nodulation of the outgoing waves isprevented. The systems T1 and T2 may be identical with transmitter T except for the modification nec; essary to produce other frequencies, or they may difler from the transmitter '1. One of these systems may, for example, be similar to that illustrated inFig. 2, and the other similar to that in Fig. 3.

,It is desirable that the antenna system a be given several degrees of freedom corresponding to the frequencies ofthe several car rier waves impressed thereon. This is con- ,veniently accomplished in one manner by tuning the antenna to the shortest wave length to be radiated which we may assume will be that of transmitter 'T. A variable capacity 18 in shunt to the aerial-ground capacity of the antenna serves to tune to the next longer wave length which welnay 'as-' sume to be that of system T'-. Y A loop resonant circuit containing inductance 19 and capaclty 20 is included 1n series with capacity 18 and is tuned to be resonant at the shortest wave length, thereby offering a high impedance to the current of these waves.

. The tuning for the "next longer wave length is accomplished by adding a capacity 21 in shunt to the capacity. 18 and providing an additional loop resonant circuit consisting of inductance 22 and capacity 23 for preventing the energy of the waves of the intermediate frequency from passing there-- ice which they are not attunedywill be allowed for in adjusting the capacities 18 and 21.

If desired, however, the antenna may .be tuned to the longest wave length, in which case, the arrangement used in Fig. 1a may be used. In this instance, tuning to the shorter wave length is accomplished by placing variable inductances 24 and 25 in shunt to the aeriaLground capacity of the antenna. By varying these inductances the desired tumng may be accomplished, the circuits 19, 20 and A 22, 23 functioning as in Fig. 1.

m Since, however, it.is-diflicult to produce variable inductances of low resistance, it may be desirable to substitute for the inductances 24 and 25, combinations of elements (Fig.

- 16) such as fixed inductances 26 and 28 in series with variable capacities 27 and 29 respectively. Each of these combinations is so designed that it will always present the required inductive reactance which may be varied by changing the capacity of the repressed upon the antenna, it is advisable to tune the antenna to the longest wave length and add auxiliary elements when tuning for the shorter wave lengths. This is becaus the radiation resistance of an ordinary antenna is greater for-shorter waves and less for longer waves. By less efi'iciently utilizing the energy of the shorter waves, the radiation for a given amount of power supplied tends to be equalized. A

An alternating current source 30 is provided to heat the cathodes of the vacuum tubes. The current is supplied through a transformer 31 across the secondary'of which the filaments of the tubes are arranged in parallel. It will be noted that'the terminals of the filaments 32 and33 which are connected to the grids are connected to opposite terminals of the alternating current source.

Thus, when the terminal of the filament 32,

which is connected 'to itsassociated grid, is

7 made positive by the alternating current the terminal of the filament 33 which is attached to its associated grid, is made negatives The same condition is' true as regards the terminals of the two filaments which are cgonnec'ted. to their respective anodes, but this is less 1mportant as the effect produced in the grid circuit is much greater. It will be seen that the distorting effect produced in the amplifying system HA by the alternating current heating source will be, to a large extent, compensated for by an equal and opposite efiect produced in thesystem HA. .VVith respect to the system V and the system O-and other sim ilar combinations of oscillator and variable impedance tubes, it makes little differences whether their filaments are oppositely or similarly connected to the heating current source.

Patent No. 1,537,941 issued'May 19, 1925.

ter T in Fig. 1. In the following description emphasis will be put upon the features distinguishing the two systems rather than the features common thereto.

Fig. 2 in general corresponds to transmit Thespeech or low frequency currents existing in the line'L, before being impressed upon the Variable impedance system V, are amplified by means'of a low frequency amplifier LA. Obviously, if the waves in line 1 are of suflicient power the amplifier LA may be omitted and the line L connected The source 1 comprises a mechanical generator; hence a filter F is provided to reduce fluctuations in the current therefrom. It will be noted that thisgiicurrent is supplied throu ha speech frequency choke C011 2 to high requency' amplifying systems HA and HA which are arrangeltl in tandem with respect to each other, but-in parallel with respect to the anode circuit of variable impedance system V. By this means the modulation is entirely effected in the high frequency amplifying systems.

The current to be modulated is supplied by an oscillation generating system 0, receiving its space current directly from the source 1. The current'generated by system Ois'amplified b the high frequency amplifying system A and impressed upon the input circuit of the system HA, of which the output circuit is-conn'ected to the sys tem HA.

The output circuit of each of the high frequency amplifying systems preferably condirectly to the input circuit-of the systgm V tains a circuit tuned by inductance and capacity to be resonant to" the same frequency as that produced by the oscillator O.

The resistance 7 and capacity 8 which are in circuit with the plate supply of the system HA function in a manner similar to the correspondingly marked elements in Fig. 1.

input circuit of the system HA likewise functionsimilarly to the elements correspondingly marked in Fig. 1.

By proper adjustment the system HA" \may be made to function entirel 'as:an'amplifier or as an amplifier and IIlOdXllfilTOI combined. No choke coils corresponding to those marked 6 in Fig. 1 are connected in circuit with the high frequency amplifying systems. -The condensers 37 are of low impedance" to high frequency and render the choke coils unnecessary; If condenser 37 of The resistance 9 and the condenser 10 in the system HA is large it also will shunt speech frequencies around oscillator 0., A suitable source 37 is provided to polarize the grids of those of the amplifiers which are not antenna will be directly connected to the output circuit of the amplifier H Another modification is .to omit the amplifying device HA of Fig. 1 and couple theradiating antenna'directly to the output circuit of the amplifying-device Device HA would then do the modulating.

Furthermore, in Fig. 2, bothof the amplifying systems HA 'and.HA' may be omitted and the oscillator O coupled directly to the input circuit of the ampllfying system HA The last-mentioned modification, however, results in a system very similar to that of Fig. 3 hereinafter described. J

Referring again to Fig. 2, it will be seen that the current Offifil'lll frequency generated by t-he oscillator cannot be appreciably varied in amplitude by any variation in condition of the variable impedance modulating system V or by any changes in capacity, impedance or resistance of the radiating antenna system. Furthermore, the currents produced in the radiating system other channels cannot react back throu the amplifiers upon the oscillating system In the system illustrated, wherein'a plate current source I is in common with the amplifier LA and the oscillator O, a reaction .from the plate circuit of the amplifier LA upon the oscillator 0 appears possible at first glance. This, however, does'not occur for 4 reasons about to be stated.

, 'ance of such a tube as is used for the oscillator The filter F, in a practical application, consists of inductances of about 1.1 hen'ries each and a shunt capacity of about 4 microfarads. The power tubes in the amplifying systems HA and HA require a plate voltage approximately twice as great as is desirable for the oscillator O. This necessitates that the resistance connectedin series with the plate supply of the oscillator 0 be aboutequal to the internal impedance of the tube itself.

Thetube of the generator 0 is small and requires a plate voltage of, for example, 350 V. and the generator l produces ahigh poten-. tial of 750V. Theaverage internal imped- O is five or six thousand ohms. The series resistance will necessarily have a similar .value of about five or six thousand ohms.

Since the impedance atmean speech frequency of the four-microfarad condenser 60 is very 10W relative to the impedance of the oscillator O in series therewith, this condenser will act as a practical short-circuit; for oscillator 0 upon. the-transformerprimary in the plate circuit of the amplifying system LA for speech frequencies. For these reasons the direct reaction from'the amplifying system .If the generator 1 is replaced by a battery or V other suorce l as illustrated in Fig. 1 having small impedance at speech frequencies then the reaction of the amplifying system LA pp'clpl theoscillator O is correspondingly neg- The oscillator 0 functions as a means for establishing a definite frequency .of carrier current. This frequency is not changed by any changes inthe constants of the antenna.

system or the amplifying systems HA, HA or HA, since these cannot react back upon the oscillator except for such negligible changes of impedances as might occur in the input circuit of amplifier HA.

Since the modulation is accomplished principally in the amplifying system HA and not at all in the amplifier HA, the frequency of the oscillator 0 does not change as the modulating wave form or its amplitude changes. Likewise, the variable impedance system V cannot act directly upon the oscillator 0 even through the plate supply source 1 because the choke coil 2 is necessarily of high inductance .and hasa very high impedance at speech frequencies.

Thefilament heating system of Fig. 2 is supplied from the alternating source 30 through the transformer 31. The secondary of the transformer 31 may be regarded as a source of heating current. Mains 38 and-39 are connected across the terminals of this secondary. A neutral connection 40 is pro-' I vided to which one terminal of each of the filaments is connected.

Where a single vacuum tube, as, for example, LA is utilized for performing one function, this may be connected from the neutral 40 to one main 39 while this is balanced by the filament of another systein, such as that ofithe system 0 connected between the neu tral 40 and the main 38; Thus, for example, it will-be seen that-the filaments of the systems O' and HA; are oppositely connected with respect to the neutral lead of the heating current supply system.

The effect produced in one of these systems tending to modulate current in accordance with. the. alternating heating current will be compensated for to a/large extent by the opposing efi'ect produced .in the other of the systems. Where, however, a plurality of tubes in parallel are used for performing a certain function, as in the systems V, HA and HA", part of the filaments may be connected across one side of the heating cur- ,filament rheostats 41, individual to each filament,'are provided.

Ordinarily, no connection from the neutral conductor 40 to any intermediate point of the secondary of the transformer 31 is essential. If, however, the two halves of the systems are seriously unbalanced, such a connection as'illustrated by the conductor 42 ma be provided.

he filament heating systems of Figs. 1 and 2 are interchangeable. A direct current filament heating system may be substituted for the alternating current filament heating system by eliminating the source 30 and the primary offlthe transformer 31, and substituting two substantially equal direct cur- The frequency of either maybe adjusted 30 not changed by means of the variable con- ,denser in the oscillatory frequency-determining circuit. The waves from either or both of these oscillators may be impressed upon the amplifier b closing one or both of the keys K and K respectively. The waves impressed upon the input circuit 51 are caused to'appear in the output circuit of the amplifier 50 with their amplitude varied in accordancerwithsignaling waves,

that is, modulated in accordance with signal in waves in a microphone circuit 52.-

e circuit 52 typifies any signalin cir-1 cuit, for example, a telephone line. A t ireeelectrode space discharge device 53 is connected in parallel with the amplifier 50 with respect to the source of current 54: which supplies energy to the anode-cathode circuit of each of the devices 50 and 53. A choke 'coil 55 having high impedance at speech frequencies maintains the sum of the currents flowing through the devices 50 and 53 constant. 1 1 v A high frequency choke coil 56 prevents high frequency ener in the anode circuit of the device 50 from eing shunted through the device 53. ,A condenser 57 of low impedance to the frequencies produced by the oscillators O and O is included in the plate circuit of the device 50 in order to prevent short-circuiting of its anode-cathode path. The amplified waves are impressed upon the radiating antenna 58 or other equivalent transmitting conductor.

When one of the oscillators and O is operating and the corresponding key K or K closed, the high frequency oscillations generated by that particular oscillator will be modulated in amplitude in accordance with speechv waves in the circuit 52 and m diated by the antenna 58. I

The frequency of the radiated waves may be changed by adjusting the frequency of the oscillator or by opening the key in its circuit and closing the key in the circuit of the other oscillator. For certain purposes, it may be desirable to radiate two high frequency waves, for example, waves having frequencies of 550,000 and 500,000 cycles respectively, each. modulated in accordance with the same signal. This occurs when both oscillators are operating and the keys K and K are both closed.

It will be seen that the frequencies of the oscillation generators are wholly independent of any variations which occur in the antenna 58, because no material reaction from the anode circuit to the grid circuit of the amplifier 50 can occur. Furthermore variations in impedance of the device 53 does not vary the frequency of the wave generated by the oscillatorO or theoscillators O and 0' when both are operating, because no appreciable energy transfer from the anode circuit to the grid circuit of the device 50 occurs. When the oscillators are once adjusted the -transmitted frequency or frequencies remain constant. 1 v

The present application comprises continuing subject matter from applicants Patents No. 1,537,941, issued May 19, 1925, and No. 1,465,358, issued August 21, 1923.

It will be apparent that some features of the invention are peculiarly adapted for use in radio systems while other features are capable of .a wider range of application and may be used in systems employing conductive lines either for signaling or for operation of mechanism from a distant-point. The novel features believed to be inherent in the invention are defined in the. appended claims. 7

What is claimed is:

1. A system comprising a thermionicrepeater having an input circuit and a plate circuit, a source of waves or impulses other than said repeater connected to said input circuit to be repeated, a modulating device, a source of current common, to and with respect to which said modulating device and said repeater are in parallel, and means-forv applying lower frequency waves or impulses to said modulating device. 2. A system comprising an electron discharge repeater, a source of waves other than said repeater connected to the input circuit thereofto be repeated, a second electron discharge repeater and means for varying the space impedance thereof at a relatively low frequency rate, a source of space current common to said repeaters and with respect to which they are in' parallel, saidsource of space current being located in a path of high r a, relatively low frequency rate, and 'means forpreventin the waves or impulses from said source 0 waves from passing through said modulating device.

, 4. The method of modulatingby means of a thermionic repeater and an impedance device which comprises producing uniform high frequency oscillations, supplying said uniform oscillations to the input circuitgmf the thermionic repeater, varying the repeating power of said repeater in accordance with the variations of potential across the impedance device,'and preventing the flow of any appreciable high frequency current throu h the impedance device.

5. modulating system comprising means for producing carrier oscillations or impulses of one frequency varying inamplitude at a lower frequency, and means reproducing the. complete amplitude variations for reducing therefrom carrier oscillations varyi g in amplitude at the same low frequency rate but having a different relation between the maximum and minimum amplitudes.

6. A modulating system comprising means for producing carrier oscillations or impulses of one frequency varying in amplitude in accordance with a signaling wave, and means for producing therefrom carrier oscillations varying in amplitude in accordance with the same signaling wave but having a higher ratio betweenthe maximum and minimum amplitudes.

7. The method of modulating which comprises successively varying the amplitude of a wave train of the same frequency in accordance with the same waves or impulses of a.

lower frequency. I

8. .The method of repeating by means of a repeater having input and plate circuits which comprises supplying a wave of nonuniform-amplitude to the input circuit of the repeater, and varying the potential impressed upon the plate circuit of the repeater in accordance with the variations in amplitudeof the non-umformiwave.

9. A system comprising an amplifying de-' vice, a second amplifying device having its input circuitconnected to the output circuit vthereof, and means for varying the amplifying power of said devices in accordance with the same series of electrical variations.

' 10. A system which comprisesmeans for varying the amplitude of a high frequency wave in accordance with a signaling wave, means for varying the electro-motlve force supplied to the plate circuit of a repeater 1n accordance Withthe same signaling wave,

means for applying a varied high frequency wave to the input circuit of the repeater, and means for causing varying leakage current in the repeater to compensate for the variations in the electro-motive-force applied to the plate circuit.

11. The method of repeating by means of a repeater having a grid circuit and a plate circuit which comprises impressing an electromotive force on the plate circuit of a repeater to cause distortion of the-repeated wave and impressing an electromotive force onthe grid circuit in amanner tending to compensate for the distortion.

12. A system comprising a source of signaling waves or impulses, a variable im-' pedance device, means for applying said waves to said device to vary the impedance thereof, a generator associated with said de vice whose oscillations are caused to vary in accordance with the impedance of said device, a repeater associated with said device whose repeating efliciencytends to vary in accordance with the impedance of said device,

means for applying to said repeater waves tude of said modulated wave is reduced, and means acting synchronously with the variations in said modulated waves tending to maintain the amplifying power of said repeater constant.

14. In combination, a highly inductive source of electromotive force, a variable impedance device and a plurality of discharge devices arranged in parallel with respect to said source, means for supplying waves of carrier frequency to the input circuit of one of said devices, and means for feeding waves ioo of said frequency from one of said devices to another thereof.

15. A highly inductive source of electrovices, means for feeding waves of said fresaid devices," and-a grid leak path associated withone' of saidplurality of devices adjusted conserving the energy of the source of the to increase the negative charge on the grid 3 thereof in -synchronism'with increases of plate potential applied to the platecircuit thereof,

I 16. The method of repeating which 'comprises supplying waves to be repeated to the grid circuit of a repeater,-caus1ng variations of a lower frequencythan said waves in the potential applied to the plate circuit of said repeater, and varying the charge on the grid of said repeater in synchronism with the lower frequency variations.

17, The combination'of a variable impedance discharge device system and an oscillation generating discharge "device system with an amplifying discharge device system, and means tending to maintain constant the sum of the currents through said systems.

- 18. The method of repeating waves which at times have a larger amplitude than at other times which comprises superimposing the waves on a unidirectional current and unidirectional current by causing the aver-' age value of the unidirectional current to vary with the amplitude of the waves to be repeated in such a manner that as one increases the other increases andas'one decreases the other decreases.

-19. A transmitting system comprlsing a space discharge device having approprlate circuits and power sources connected there-' to whereby its functions as'a generator of carrier frequency waves, an amplifier in which the energy generated by said generator is amplified, a' transmitting conductor system supplied by said amplifier, said amplifier having a spare current circuit, and a signal-controlled. variable impedance device connected in shunt to aportion of said circuit.- v j 20. A" transmitting systemcomprising a space, discharge devlce having appropriate circuits and power sources connected'thereto whereby it functions asea generator of carrier frequency waves, an amplifier controlled by said waves for producing waves of the same frequency and increased power, a radiating antenna system supplied with waves of increased power by'said amplifier, saidamplifier having an anode-cathode circuit, a variable impedance device connected in shunt to a portion of said circuit, and a speech frequeucy circuit for controlling the impedance of the variable impedance device. 1 21. A radio system comprising an amplifier, an anode-cathode circuit therein, a variable impedance device associated with said amplifier, a common source of current for said device and said amplifier, means for maintaining constant the sum of the current supplied from said source to sald device 'que'ncy .waves connected to the input circuit of said amplifier.

22. A-radio transmitting system co 'nprising a frequency-setting oscillation generator of low power, an amplifying device for='--increasing the power of the waves produfi bd,

signal-controlled variable impedance means in shunt to the output circuit of said am= plifier, means tending to maintain constant the sum of the currents supplied to said-am plifier and variable impedance means, and a radiating antenna u on which the -waves from the output circult'of said amplifier-are impressed.

23.- A'tllQIHllOHlC system comprising adis charge device and appropriate circuits whereby said device functions as a enerator of oscillations, a second device a aptedflto, function as a repeater to repeat the generatedoscillations, filaments in said devices, an alternating current heating source for the filaments of said devices, and means whereby the disturbing 'efi'ect produced by said source upon one of said devices is compensated for by the effect produced upon the pther of said devices. a

24. A system for multiplexing a radio telephone system comprising an antenna tuned to a certain transmitting wave length, an additional capacity connected in parallel to the aerial-ground .capacity of said antenna fortuning said antenna to another longer wave I length, and a loop circuit in series with said additional capacity tuned to offer a very high impedance to currents corresponding to said first mentioned wave length.

25. A transmission system comprising means for impressing on an antenna signallng waves of different frequencies, tumng elements for tunlng said antenna to one of said frequencies, additional tuning elementsarranged in shuntbranches to tune said antenna 'to each of said other, frequencies respectively, and impedance means in series with each additional tuning element to prevent the passage therethrough of the waves of-an adjacent frequency.

26. A signaling system comprising an antenna tuned to a given frequency, means for impressing currents of said frequency and a series of other frequencies upon said antenna, a series of branch circuits each of which comprises tuning means for tuning said antenna to one other said series of frequencies, and an impedance means offering high impedance to one other of said'series of frequencies, the

first of said branch circuits being in shunt to V the radiating capacity of said antenna and antenna to the one of said waves having the lower frequency, a shunt circuit for tuning said antenna circuit to said wave of higher frequency, and means in said shunt circuit ofiering a high impedance to said waves of lower frequency, whereby the radiating efiiciency of said antenna system for said waves tends to be equalized.

28. An antenna circuit, means for conveying waves tosaid antenna to be transmitted including a discharge device having its output circuit coupled to said antenna, said output circuit being tuned to resonance to the waves to be transmitted, and paths in shunt to said output circuit corresponding to other waves to be im ressed upon said antenna, each being tune to offer low impedance to one of said other waves.

29. A multiplex transmission system comimpedance to waves'of the frequency or frequencies that are to be transmitted by said circuit, and paths in shunt to said first mentioned path of low impedance to the waves to be transmitted by each of said other transmission circuits.

31. A system for modulating by means of a vacuum tube having-a grid circuit and a, plate circuit which comprises means for impressing an electromotive force ofmodulating frequency on the plate Ici'rcuit'and means for changingthe potential of'the grid of said device inopposite phaserelationwith respect to said force of'modulating frequency; 32.'A vacuum tube amplifymgsystem for radio frequency currents comprisingat least two tubes in tand''m, and means for coupling the plate-filament circuit of one of said tubes" to the grid-filament circuit of the next suc-' *ce'eding tube comprising an impedance ele ment in the plate-filament circuit of the first tube through which high frequency currents are caused to flow to set up high frequency voltages across the grid-filament'circuit of the second tube, a choke coil of suflicient impedance at frequencies to be amplified for preventing high frequency variations from passing therethrough located in series with the space current path of said first tube, and

a condenser having one terminal connected to the common point of said choke coil and the plate of said first tube and the other terminal to a point on said impedance element remote from the filament of said first tube.

33. In a wave signaling system, means for generating continuous high frequency carrier oscillations, an amplifier for amplifying said carrier oscillations, a source of uni-directional voltage for said amplifier, a variable impedance in series in a direct current circuit with said source of voltage, means for keeping the current from said source substantially constant, and means for varying said impedance in accordance with signals.

34. In a wave signaling system, a generator of high frequency oscillations having an output circuit, a vacuum tube amplifier for amplifying said high frequency oscillations, said amplifier having an input circuit and an output circuit, said input circuit being associated with the said output circuit of said generator, a source of current in the output circuit of said amplifier, a variable resistance in shunt to sa1d source of current, and means for varying said resistance in accordance with signals.

7 35. In a wave signaling system, a generator of continuous high frequency oscillations of constant amplitude, an output circuit for said generator, a vacuum tube amplifier having input electrodes and output electrodes, an input circuit for said amplifier, said input circuit being associated with the output circuit of said generator, an output circuit for said amplifier including said output electrodes, a load circuit associated with said output circuit, a source of uni-directional current included in the output circuit of said amplifier, an inductance coil in series with said source of current and included in said output circuit said coil being operable to maintain the flow of current from said source substantially constant, a second vacuum tube comprising a plate, a grid and a filament, said plate and filament being connected in series with said source of current and said inductance coil and in shunt to the output electrodes of said amplifier, an input circuit input circuit and operable to vary the impedance between the plate and filament of said second vacuum tube inaccordance with signals to be transmitted, the arrangement being such that continuous high frequency oscillations from said generator are amplified by said amplifier and simultaneously modulated by-diversion of current from said amplifier iit accordance with signals impressed on said microphone and furthermore that the frequency of said oscillations is sub siantially uuazl'ccrcd by variations in the constants of said load circuit.

36. The method of produing signal modulated high frequency carrier "iZY'vif of substantially uniform frequency whim consists in generating unmodulatcd high frequency carrier current of substantially con- 'said current away from said amplifierv in accordance with signals to be transmitted.

37: In a wave signalingsystem, means for generating continuous high frequency carrier oscillations, an amplifier for amphfying said carrier osclllations, said means for genoscillations from said generator are ampli-.

fied by said am lifier and simultaneously 7 modulated by iversion .of current from said amplifier in accordance withsignals impressed on said microphone and furthermore that the frequencyof said oscillations crating comprising a vacuum tube system. is substantially unaffected by variations in generator producing continuous high frequency oscillations of substantially constant amplitude and frequency whereby such oscillations are supplied unmodulated to the" modulating amplifier, a source of uni-directional voltage for said am lifier, a variable im edance in series in a irect current ci-rcult with said source of voltage, means for keeping the current from said source substantially constant, and means for varying said impedance in'accordance with signals.

38. In a wave signaling system, a genera tor of high frequency oscillations having an output circuit, a vacuum tube-amplifier for amplifying said high frequency osclllatlons, said .amplifier having an input circuit and an output circuit, said input circuit being as sociated with the said'output'circuitof said generator, a source ofcurrent in the output circuit of said amplifier, a variable resistance in shunt to said source'of current, and means for varying said resistance in accordance with signals, said generator comprising a vacuum tube system generator producing continuous high frequency oscillations of substantially constant amplitude and A frequency, whereby such oscillations are supplied unmodulated to the modulating ampli-- 39. In a wave signaling system,a' generator of continuous h1 h frequency oscillations of constant amplitu e, an output'circuit for said generator, a vacuum tube amplifierhaving input electrodesand output electrodes, an. input circuit for said amplifier, said input circuit beingassociated with the output circuit'of said generator, an output circuit for said amplifier including said out 'ut elec-.

trodes, a load circuit associated with said output circuit, a source of uni-directional current included in the output circuit of said amplifier, an inductance coil in series with said source of current and included in said output circuit said coil being operable to maintain the flow'of current from said source substantially constant, a second vacuum tube comprising a plate, a grid and a filament, said plate and filament being connected in series with said source of current and said inductance coil and in shunt to the output electrodes of said amplifier, an in ut circuit for said second vacuum tube an a microphone associated with said last mentioned the constants of said load circuit, said generator comprising a vacuum tube system generator producing continuous high frequency oscillations of substantially constant amplitude and frequency, whereby such oscilla- "tions are supplied unmodulated to the modulating amplifier.

40. The method of producing signal modulated high frequency carrier current of substantially uniform frequency which consists in generating unmodulated high frequency carrier current of substantially constant fre-- quency by employing a vacuum tube system generator. producing continuous high frequency oscillations of substantially constant amplitude and frequency, impressing said unmodulated carrier current upon the input j circuit 01% an-amplifier,supplyingcurrentof substantially constant value to the output circuit of said amplifier, andvariably divertmg said current away from said amplifier in accordance wih si als to be transmitted.

41. The method 0 varying the amplification of. a vacuum ube amphfier which consists in adjusting the static grid potential ilglaccorianlee vvlith the amplitude of the env ope'o t e t ernat' 1n ut ener a plied to the tube. mg p j gy 42. Themethod ofo ratingatranslatin circuit, including a tlifee-element vacuum t which consists in so cont'ro the static gridpotential of the-vacuum tu in accordance with the m 'tude'of the envelope of the-"alternating 1nput energy that a predetermined relation between the input energy applied to the system and the output energy from the system will be obtained. 43. The method of operating a translating circuit, including a three-element vacuum tu'be, which consists in so controlling the static potential of the grid of the tube in accordance with the amplitude of the envelope of the alternating input energy that the output energy will be a maximum for a predetermined amplitude pf the input en-.

ergy. Y

44. -Themethod of operating a translating circuit, including a three-element vacuum tube, which-consists in so controlling the static potential of the grid of the tube in accordance with the amplitude of the input energy that the system will discriminate tube amplifier which consists in shifting the.

having amplitudes greater than a predetermined amplitude.

46. The method ofoperating a vacuum operating point of the tube along its characteristic axis in accordance with the amplitude of the envelope of the alternating input energy.

47. In a translating system, a three-ole ment vacuum" tube, means to apply energy variations to said tube and means to adjust the working point of said tube along its characteristic axis in accordance with the amplitude of the envelope of the alternating energy variations.

' 48. In a wave signaling system, a generator of high frequency oscillations having an rent in the output circuit of said amplifier, a I

output circuit, a vacuum tube amplifier for amplifying said high frequency oscillations, said amplifier having an input circuit and an output circuit, said input circuit including a leak resistance shunted by a condenser and being associated with the said output circuit of the saidgenerator, a source of ourvariable resistance in shunt to said source of current, and means for varying said resistance in accordance with signals.

' In witness whereof, I hereunto subscribe my name this 29th day of December, A. D.

- RAYMOND A. HEISING. 

